There has been significant effort in the last decade or so to develop systems for identification of products, either identification of a particular product from a product signature or identification of products moving through a defined space. This effort has resulted in a number of product identification systems utilizing various technologies to generate and evaluate product identification signals. One of the most widely used system utilizes a bar code reader response to a bar coded element carried by a product or article. As the bar coded element moves through a scanning field, the response to the scanning field changes and this change is detected. Such systems are primarily intended only for identification of products or articles moving through a defined space, although there is no technological limitation to generate identification signatures. These systems are restricted in the areas of utilization due to size and cost restraints.
Other known systems utilize transponder tags carried or otherwise attached to a product or article. Many of these transponders are expensive and have a limited range of detection, typically, less than one meter. There is no known transponder tag detection system that utilizes harmonic detection for article identification. Again, transponder tags have found limited use due to the size of the transponder and the cost of a tag that may be utilized once and discarded.
In addition to monitoring and tracking articles and products, identification systems presently in use also find utility in security applications. This includes document security where size of the tag has a more significant impact than tags used for article and product identification for monitoring and tracking. Systems presently in use for article identification including product identification and document identification do not provide a security identification signature or “fingerprint” for a document. The use of an identification signature enables the recognition of individual articles or articles in groups identified with a common identification signature.
Thus, there is a need for an article identification system utilizing a relatively inexpensive tag or detector element and having a size that does not burden the article for identification. Further, there is a need for an article identification system utilizing a tag that provides an identified signature to separate identified articles into classes.